Recently, an endoscopic surgical procedure such as an endoscopic mucosal resection (EMR) and an endoscopic submucosal dissection (ESD) for an inside of a stomach has become available with the improvement of an endoscopic technology. After the endoscopic surgical procedure of the inside of the stomach, bleeding in a surgical site is stopped; however, because there is a possibility that the surgical site bleeds again at night, it is required to monitor an existence of the bleeding. Conventionally, as a method of monitoring the existence of the bleeding inside the stomach, a tube with a continuous length from the inside of the stomach to the outside of a body of a patient is inserted from a nose or a mouth and placed inside the stomach to monitor whether blood comes out of the body through the tube.
As a technology for detecting a status of the inside of a body cavity, for example, a technology for placing an indwelling capsule at around a pyloric by attaching a string to the pH-sensor indwelling capsule and fixing the end portion of the string to a region around teeth or a mouth is disclosed according to Patent Document 1. Patent Document 2 discloses a technology for sensing a physiological parameter of the inside of an esophageal region by placing a sensor capsule to a sensing target region inside the esophageal region of an examinee. Patent Document 3 discloses a technology for fixing a medical capsule to the inside of the body cavity by attaching a clip to the medical capsule and by clipping body tissue inside the body cavity by the clip.    Patent Document 1: Japanese Patent Application Laid-Open No. H6-63051    Patent Document 2: U.S. Pat. No. 6,285,977 Specification    Patent Document 3: Japanese Patent Application Laid-Open No. H5-23322